Looking from the fort platform,across the double ditch fort defences, across the stream, to the Antonine Wall and formidable Wall ditch.In shot,the wooden bridge over the stream,roughly equates with the base of the Wall ditch,seen coming down the hill from the west.The arisings from the ditch excavation,were cast out to the north of the wall ditch,so as to form a glacis,angled such that any attacker could find nowhere to hide from Roman slingshot and arrows.In that respect,the same as on Hadrian's Wall.
see http://www.google.co.uk/imgres?imgurl=http://www.undiscoveredscotland.co.uk/falkirk/roughcastle/images/roughcastle-450.jpg&imgrefurl=http://www.undiscoveredscotland.co.uk/falkirk/roughcastle/&h=338&w=450&sz=57&tbnid=acnFlLrR_bfqOM:&tbnh=107&tbnw=142&zoom=1&usg=__8TS_en4F4UhMgAGIdOdtyoRzy2g=&docid=istNh933KmAx2M&sa=X&ei=vpIhUrCrIOq00wXvv4C4DQ&ved=0CFsQ9QEwAQ&dur=10227